This invention relates to a load-lock chamber suitably usable in an exposure apparatus which uses ultraviolet light as exposure light and which is arranged to replace the interior of the apparatus by an inactive gas and also which has a function for transferring a pattern of a mask onto a photosensitive substrate through a projection optical system, wherein the load-lock chamber is adapted to be operated continuously. In another aspect, the invention concerns an exposure apparatus having such a load-lock chamber and an exposure method that enables continuous operation.
Conventionally, the procedure of manufacturing semiconductor devices comprising very fine patterns such as LSI or VLSI uses a reduction type projection exposure apparatus which functions to project and photoprint, in a reduced scale, a circuit pattern formed on a mask onto a substrate being coated with a photosensitive material Increases in the density of the semiconductor device have forced further miniaturization, and advancement in the resist process as well as improvement of the exposure apparatus to meet the miniaturization have been pursued.
The resolving power of an exposure apparatus can be improved by, for example, shortening the exposure wavelength used or by enlarging the numerical aperture (NA) of a projection optical system.
As regards the exposure wavelength, recently, in place of i-line (365 nm), KrF excimer lasers having an emission wavelength of about 248 nm or ArF excimer lasers having an emission wavelength of about 193 nm have been developed. Further, fluorine (F2) lasers having an emission wavelength of about 157 nm are being developed.
In regard to deep ultraviolet light, particularly, ArF excimer lasers having a wavelength of about 193 nm or F2 excimer lasers having an emission wavelength of about 157 nm, it is known that there is an oxygen (O2) absorption band in the regions about these wavelengths
For example, because of its short wavelength (157 nm), the applicability of fluorine excimer lasers to exposure apparatuses have been attempted. However, the wavelength of 157 nm is present in a range of a wavelength region generally called a vacuum ultraviolet. In such wavelength region, the absorption of light by oxygen molecules is large. As a result, the atmosphere does not transmit most of the light. Therefore, this light source can be used only in a situation that the atmospheric pressure is reduced close to vacuum and that the oxygen concentration is sufficiently lowered. According to xe2x80x9cPhotochemistry of Small Moleculesxe2x80x9d, Hideo Okabe, A Wiley-Interscience Publication, 1978, p178, the absorption coefficient of oxygen to light of a wavelength 157 nm is about 190 atmxe2x88x921cmxe2x88x921. This means that, when light of a wavelength 157 nm passes through a gas having an oxygen concentration of 1%, under a unit atmospheric pressure, the transmission factor T per 1 cm is only:
T=exp(xe2x88x92190xc3x971 cmxc3x970.01 atm)=0.150.
Further, as the oxygen absorbs the light, ozones (O3) are produced. Various products are created by ozones, and they are deposited to surfaces of optical elements to decrease the efficiency of the optical system.
In consideration of them, in projection exposure apparatuses which use deep ultraviolet rays such as an ArF excimer laser or a F2 excimer laser, purging means such as an inactive gas (e.g., nitrogen or an inert gas) is provided at the light path of an exposure optical system, to suppress the oxygen concentration at the light path to a low level of an order of a few ppm or less.
As described above, in exposure apparatuses using deep ultraviolet light, particularly, an ArF excimer laser having a wavelength of about 193 nm or a fluorine (F2) excimer laser having a wavelength of about 157 nm, because the ArF excimer laser light or F2 excimer laser light is very easily absorbed by a substance, the light path must be purged to a level of an order of a few ppm or less. Further, this is also the case with the moisture (H2O). It should be reduced to a level of a ppm order.
In order to meet this, conventionally, the inside of an exposure apparatus, more particularly, the portion thereof defined for a light path of ultraviolet light, is purged by use of an inactive gas. Further, a load-lock mechanism is provided at a portion for connecting the inside of the exposure apparatus with the outside thereof. When a reticle or a wafer is to be loaded from the outside, the outside atmosphere is once isolated by the load-lock mechanism. After impurities inside the load-lock mechanism are purged by an inactive gas, the reticle or wafer is introduced into the exposure apparatus.
FIG. 1 is a schematic and sectional view of an example of a semiconductor exposure apparatus having a fluorine (F2) excimer laser as a light source and also a load-lock mechanism.
Denoted in FIG. 1 at 1 is a reticle stage on which a reticle having a pattern formed thereon is placed. Denoted at 2 is a projection optical system for projecting the pattern of the reticle onto a wafer. Denoted at 3 is a wafer state for carrying a wafer thereon and being movable in the X, Y, Z, xcex8 and tilt directions. Denoted at 4 is an illumination optical system for projecting illumination light onto the reticle, and denoted at 5 is a light directing optical system for directing light from the light source to the illumination optical system 4. Denoted at 6 is a fluorine (F2) excimer laser unit which is a light source, and denoted at 7 is a masking blade operable to block exposure light so as to prevent those regions on the reticle, other than a pattern region thereof, from being irradiated with the exposure light. Denoted at 8 and 9 are casings for encircling an exposure optical axis around the reticle stage 1 and the wafer stage 3. Denoted at 10 is a He gas conditioning machine for adjusting the inside of the illumination optical system 4 and the projection optical system 2 to provide there a predetermined He ambience. Denoted at 11 and 12 are N2 gas conditioning machines for adjusting the inside of the casings 8 and 9 to provide there a predetermined N2 ambience. Denoted at 13 and 14 are a reticle load-lock and a wafer load-lock, respectively, to be used when a reticle and a wafer are to be loaded into the casings 8 and 9, respectively. Denoted at 15 and 16 are a reticle hand and a wafer hand, respectively, for conveying a reticle and a wafer, respectively. Denoted at 17 is a reticle alignment mark to be used for adjusting the position of the reticle. Denoted at 18 is a reticle storage unit for storing plural reticles inside the casing 8. Denoted at 19 is a prealignment unit for performing prealignment of a wafer.
FIG. 2 is a schematic and sectional view of another example of a semiconductor exposure apparatus having a fluorine (F2) excimer laser as a light source and also a load-lock mechanism.
In the exposure apparatus of FIG. 2, the exposure apparatus as a whole is covered by a casing 20, and O2 and H2O there are purged by a N2 gas. Denoted at 21 is an N2 gas conditioning machine for providing a N2 ambience in the whole casing 20. In this exposure apparatus, the inside spaces of a barrel 2 and an illumination optical system 4 are isolated from the inside space of the casing 20 (driving system space), and they are adjusted independently so that a He ambience is provided there. Denoted at 13 and 14 are a reticle load-lock and a wafer load-lock, respectively, to be used when a reticle and a wafer are loaded into the casings 8 and 9, respectively.
FIG. 3 is a schematic view of an example of a semiconductor manufacturing system including an exposure apparatus such as shown in FIG. 1 or 2, as well as a coating and developing machine.
Denoted in FIG. 3 at 22 is a coating and developing machine including a coater unit for coating a wafer with a resist material, and a developing unit for developing a wafer after being exposed. Denoted at 23 is an exposure apparatus, and denoted at 24 is an interface unit operable for transfer of a wafer between the coating and developing machine 22 and the exposure apparatus 23. Denoted at 25 and 26 are in-line ports, and denoted at 28 and 29 are manual loading and unloading ports. Each of these ports is provided with a load-lock mechanism as well as a function for introducing a N2 gas. At a prealignment unit 19, for prevention of inaccurate measurement due to expansion or contraction of a wafer, the prealignment operation is performed to a wafer being controlled at a predetermined temperature. Denoted at 27 is a wafer temperature adjusting unit for adjusting a wafer to a predetermined temperature described above.
As has been described hereinbefore, in an exposure apparatus using ultraviolet light, more particularly, ArF excimer laser light or fluorine (F2) excimer laser light, since absorption of light at the wavelength close to the emission wavelength of the ArF excimer laser light or F2 excimer laser light, by oxygen or moisture, is large, the oxygen and moisture content concentration should be lowered so as to obtain a sufficient transmission factor and a good stability. In order to control the concentration of them exactly, a load-lock mechanism is provided in a portion connecting the inside and outside of the exposure apparatus. When a reticle or a wafer is to be loaded from the outside, it is once isolated from the outside temperature. After impurities within the load-lock mechanism are purged by an inactive gas, the reticle or the wafer is introduced into the exposure apparatus.
As described, conventionally, in order to assure a good transmission factor to fluorine (F2) excimer laser light and a good stability thereof, a wafer stage (or a reticle stage) as a whole, containing a projection lens end face and a distance measuring interference optical system, is accommodated in a gas-tightly closed chamber. The inside of the chamber is purged by a high-purity inactive gas. Additionally, in order that a reticle or a wafer can be loaded into the closed chamber while maintaining a constant inactive gas concentration or a constant gas pressure inside the chamber, a load-lock chamber is provided adjacent the closed chamber. However, the load-lock chamber has a volume for accommodating about ten to twenty wafers therein, and the purging by an inactive gas is carried out while plural wafers are stored therein. It requires therefore a long time until a predetermined inactive gas concentration is accomplished. This leads to a decreased productivity of the exposure apparatus.
Further, the load-lock chamber requires a door for strictly isolating the outside atmosphere. It takes a substantial time for the opening and closing motion of the door. Also, the need for a space for the opening and closing motion of the door makes the whole size of the apparatus bulky.
It is therefore desirable to develop a load-lock mechanism by which the volume of the space for accommodation of wafers can be made very small, by which the purge time required until a predetermined inactive gas ambience is accomplished can be shortened, by which degradation of the inactive gas concentration in the load-lock chamber can be avoided, and by which the productivity of the apparatus can be improved
It is accordingly an object of the present invention to provide a continuous load-lock chamber to be suitably used in an exposure apparatus which uses ultraviolet light as exposure light, in which the inside of the apparatus is replaced by an inactive gas, and in which a pattern of a mask is transferred, by projection exposure, onto a photosensitive substrate through a projection optical system.
In accordance with an aspect of the present invention, there is provided a load-lock chamber for loading and unloading a reticle or a wafer into and out of an exposure apparatus, comprising: a table having a slotted flat plane for carrying thereon one or more reticles or wafers; a combination of an elevation shaft and an elevation driving unit, for moving said table upwardly and downwardly; a receiving bore for receiving said table with a small clearance maintained between the bore and a side wall of said table; and a load-lock chamber main assembly operable to move said table into said bore and to accommodate or discharge said table with a reticle or a wafer being carried thereon.
In one preferred form of this aspect of the present invention, the load-lock chamber may further comprise one or more purging inactive gas flowpassages provided on a side face of the bore of said load-lock chamber main assembly, to be opposed to said table, so that an inactive gas can be supplied to the slotted flat plane of said table, for carrying a reticle or a wafer thereon.
The one or more purging inactive gas flowpassages may be disposed radially around the bore of said load-lock chamber main assembly.
Each of said purging inactive gas flowpassages may have a purging inactive gas supplying port and a purging inactive gas outlet port
The load-lock chamber may further comprise one or more purging inactive gas flowpassages provided on a side face of said table, to be opposed to the bore of said load-lock chamber main assembly, so that an inactive gas can be supplied to the slotted flat plane of the table for carrying thereon a reticle or a wafer.
The load-lock chamber may further comprise one or more inactive gas grooves for static pressure bearing, provided on a side face of said table to be opposed to the bore of said load-lock chamber main assembly, so as to enable non-contact movement of said table, while preventing flow of an outside air into the space of the slotted flat plane during the gas purging.
The or each inactive gas groove may be an annular groove formed around said table.
The load-lock chamber may further comprise one or more inactive gas grooves for static pressure bearing, provided on a side face of the bore of said load-lock chamber main assembly, to be opposed to said table, so as to enable non-contact movement of said table, while preventing flow of an outside air into the space of the slotted flat plane during the gas purging.
The or each inactive gas groove may be an annular groove formed around the bore of said load-lock chamber main assembly.
Here, the static pressure bearing gas groove may be omitted. The small clearance between the bore and the table may be assured by a separate bearing structure. A labyrinth seal groove may be formed on one of or both of opposed faces of the bore and the table, to enable non-contact motion of the table, while preventing flow of an outside air into the space of the slotted flat plane during the gas purging.
Further, the load-lock chamber main assembly may have a cylindrical shape.
The elevation shaft may be rotatable.
In accordance with another aspect of the present invention, there is provided an exposure apparatus for transferring a pattern of a reticle onto a wafer through a projection optical system and by use of ultraviolet light as exposure light, wherein the inside of said apparatus is replaced by an inactive gas, characterized by a load-lock chamber as recited above, for loading and unloading a reticle or a wafer into or out of said apparatus.
In one preferred from of this aspect of the present invention, the number of said load-lock chamber may be single, and wherein said load-lock chamber may function both for the loading and unloading of the reticle or the wafer.
The number of said load-lock chamber may be two or more, wherein each of the two or more load-lock chambers may function both for the loading and unloading the reticle or the wafer, or the two or more load-lock chambers function for the loading and the unloading of the reticle or the wafer, respectively.
The ultraviolet light may be laser light from a laser light source.
The laser light source may be a fluorine excimer laser.
The laser light source may be an ArF excimer laser.
The inactive gas for replacing a light path of the exposure light may contain one of nitrogen, helium and argon.
The exposure apparatus may further comprise purging means effective to fill the inside of said apparatus with an inactive gas.
In accordance with a further aspect of the present invention, there is provided an exposure method for transferring a pattern of a reticle onto a wafer through a projection optical system and by use of ultraviolet light as exposure light, wherein the inside of an apparatus is replaced by an inactive gas, characterized by use of a load-lock chamber as recited above, for loading and unloading a reticle or a wafer into or out of the apparatus.
In one preferred form of this aspect of the present invention, one or more load-lock chambers may be used, wherein the or each load-lock chamber may function both as a loading port and an unloading port.
Plural load-lock chambers may be used each being operable both as a loading port and an unloading port, wherein the load-lock chambers may be used with a shift at every step for the loading and unloading, to thereby enable successive exposures.
Plural load-lock chambers may be used separately as an exclusive loading port and an exclusive unloading port, respectively.
The load-lock chambers having a function as an exclusive loading port may have a plurality of slots which are used while being shifted at each step, wherein the load-lock chambers having a function as an exclusive unloading port may have a plurality of slots which are used while being shifted at each step, whereby successive exposures are enabled.
The exposure method may further comprise (i) loading a reticle or a wafer into a load-lock chamber, (ii) moving an elevation table upwardly or downwardly, (iii) purging the inside of the load-lock chamber, (iv) unloading the reticle or the wafer and moving it into an exposure apparatus.
In accordance with a yet further aspect of the present invention, there is provided a semiconductor device manufacturing method, comprising the steps of: providing a group of production machines for various processes, including an exposure apparatus as recited above, in a semiconductor manufacturing factory; and producing a semiconductor device through plural processes using the production machine group.
The method may further comprise (i) connecting the production machines of the group with each other through a local area network, and (ii) executing data-communication concerning information related to at least one production machine of the production machine group, between the local area network and an external network outside the semiconductor manufacturing factory.
A database provided by a vendor or a user of the exposure apparatus can be accessed through the external network so that maintenance information related to the production machine can be obtained through the data communication, and wherein production control can be performed on the basis of data communication made through the external network and between the semiconductor factory and a separate semiconductor factory.
In accordance with a still further aspect of the present invention, there is provided a semiconductor manufacturing factory, comprising: a group of production machines for various processes, including an exposure apparatus as recited above; a local area network for connecting the production machines of the production machine group with each other; and a gateway for enabling an access from the local area network to an external network outside the factory; wherein information related to at least one production machine in the group can be data communicated by use of the local area network and the gateway.
In accordance with a yet further aspect of the present invention, there is provided a method of executing maintenance for an exposure apparatus as recited above and being provided in a semiconductor manufacturing factory, said method comprising the steps of: preparing, by a vendor or a user of the exposure apparatus, a maintenance database connected to an external network outside the semiconductor manufacturing factory; admitting an access from the semiconductor manufacturing factory to the maintenance database through the external network; and transmitting maintenance information stored in the maintenance database to the semiconductor manufacturing factory through the external network.
The exposure apparatus may further comprise a display, a network interface and a computer for executing a network software, wherein maintenance Information related to said exposure apparatus is data communicated through the computer network.
The network software may provide on the display a user interface for accessing a maintenance database prepared by a vendor or a user of said exposure apparatus and connected to an external network outside a factory where said exposure apparatus is placed, thereby to enable obtaining information from the database through the external network.
The load-lock chamber described above may further comprise a labyrinth seal groove formed on one or or both of a side face of the bore of said load-lock chamber main assembly and a side face of said table to be opposed to the bore.
The labyrinth seal groove may comprise a plurality of annular grooves.
These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.